基于多级等压混合的引射器参数匹配与优化

匹配和优化多级等压混合引射器的各项参数,得到理想的引射器增压比和引射效率,目的是提高多级等压混合引射器性能。通过数学分析和实验,研究了单级引射器参数变化对性能的影响,明确了多级等压混合引射器级数的确定原则,对影响单级引射器性能的参数在多级中进行了匹配和优化,表明引射马赫数、被引射气体温度、单级引射器引射系数和增压比匹配与优化后,能显著提升多级等压混合引射器性能。     

EVA worksite analysis—Use of computer analysis for EVA operations development and execution

To sustain the rate of extravehicular activity (EVA) required to assemble and maintain the International Space Station, we must enhance our ability to plan, train for, and execute EVAs. An underlying analysis capability has been developed to ensure EVA access to all external worksites as a starting point for ground training, to generate information needed for on-orbit training, and to react quickly to develop contingency EVA plans, techniques, and procedures. This paper describes the use of computer-based EVA worksite analysis techniques for EVA worksite design. EVA worksite analysis has been used to design 80% of EVA worksites on the U.S. portion of the International Space Station. With the launch of the first U.S. element of the station, EVA worksite analysis is being developed further to support real-time analysis of unplanned EVA operations. This paper describes this development and deployment of EVA worksite analysis for International Space Station (ISS) mission support.     

Observations of birkeland currents

Recent measurements of precipitating energetic particles and vector magnetic fields from satellites and sounding rockets have verified the existence of geomagnetically-aligned electric currents at high latitudes in the ionosphere and magnetosphere. The spatial and temporal configuration of such currents, now commonly called Birkeland currents, has delineated their role in providing ionospheric closure of magnetospheric current systems, and gross features of these current systems may be understood in terms of theoretical models of magnetospheric convection. The association of Birkeland currents with auroral features on a very small scale suggests that auroral acceleration may result from the current flow.     

Radio science investigations with Voyager

The planned radio science investigations during the Voyager missions to the outer planets involve: (1) the use of the radio links to and from the spacecraft for occultation measurements of planetary and satellite atmospheres and ionospheres, the rings of Saturn, the solar corona, and the general-relativistic time delay for radiowave propagation through the Sun's gravity field; (2) radio link measurements of true or apparent spacecraft motion caused by the gravity fields of the planets, the masses of their larger satellites, and characteristics of the interplanetary medium; and (3) related measurements which could provide results in other areas, including the possible detection of long-wavelength gravitational radiation propagating through the Solar System. The measurements will be used to study: atmospheric and ionospheric structure, constituents, and dynamics; the sizes, radial distribution, total mass, and other characteristics of the particles in the rings of Saturn; interior models for the major planets and the mean density and bulk composition of a number of their satellites; the plasma density and dynamics of the solar corona and interplanetary medium; and certain fundamental questions involving gravitation and relativity. The instrumentation for these experiments is the same ground-based and spacecraft radio systems as will be used for tracking and communicating with the Voyager spacecraft, although several important features of these systems have been provided primarily for the radio science investigations.     

Counterstreaming hydrogen and oxygen ions observed in the magnetosphere on ISEE-1

Counterstreaming ions or ions travelling simultaneously both parallel and antiparallel to the magnetic field direction have been briefly noted in the literature but have not been studied previously in depth. We have studied over 60 counterstreaming ion (CSI) events observed on the ISEE-1 satellite. They were found to occur at altitudes of about 2 to 8 Earth radii on L shells of about 5 to 12 in the evening-to-morning sector from about 1700 - 0900 LT. Often both oxygen and hydrogen ions at a number of energy levels are counterstreaming but some events show only either oxygen or hydrogen ions involved. One particularly interesting event shows only counterstreaming oxygen ions with 417 eV energy; oxygen ions of lower energy (215 eV) and above (630–17000 eV) and all the hydrogen ions between 215–17000 eV energy have lower fluxes and/or nearly isotropic pitch angle distributions. This event correlates well with wave activity in the 17–100 Hz band and is also accompanied by 200 eV downgoing and 400 eV upgoing electrons. Details of this event and the other counterstreaming events are presented.     

A new reeling technique for very long extension scanning in the stratosphere

A balloon borne winching system has been developed for extending a very long tether with payload down into the stratosphere and recovering it; this has been flight proven by being carried to an altitude of 40 km, lowering a 62 kg stratospheric photochemistry experiment 12 km at a descent velocity of ～6–8 m/sec and recovering it at comparable velocities. During the first flight, data gave no evidence of dynamic instabilities due to the system or the stratospheric interactions. The future utility of this payload is discussed with attention to the design factors that bound the range of performance of this type of system.     

Water Vapor Imagery: A New Observation for Weather Analysis

Water vapor imagery is now available routinely from weather satellites for use in meteorological operations. Research during the past 5 years has provided insight concerning the physical interpretation of this data under varying atmospheric moisture and temperature distributions. Investigations have also identified new applications for use in operational weather analysis and forecasting. The water vapor patterns and the changes of these patterns with time, relate to upper tropospheric flow, the jet stream, tropopause breaks, the intensification of thunderstorms, and tropical storm motion. Animated hourly water vapor imagery will become available next year for use by National Weather Service (NWS) field forecasters. It will provide them with a new diagnostic tool for short range forecasts.     

基于Gauss平均引数的RNAV进近程序航迹引导参数计算

为准确计算基于WGS-84坐标的RNAV进近程序航路点坐标和航迹引导参数,提供精密RNAV导航数据,降低RNAV进近系统误差,提出了实测跑道入口WGS-84坐标,然后沿跑道中线外推各航路点WGS-84坐标的计算方法。采用Gauss平均引数法对各航段的航线角及航段距离进行了反算,以验证外推航路点坐标的计算精度。通过西南地区某机场＂T＂型RNAV进近程序的设计及飞行验证,该方法可推广到其他机场的RNAV进近程序设计。     

Factors controlling activity of zirconia-titania for photocatalytic oxidation of ethylene.

Small photocatalytic devices were developed to remove ethylene from closed plant growth units flown in space. The devices utilized sol-gel-derived catalyst pellets of zirconia-titania. This study was undertaken to understand the significance of different factors on the photocatalytic activity of the catalyst. Increasing reaction temperatures and decreasing humidity of the air significantly increased oxidation of ethylene. The quantity of ethylene oxidized per unit time increased linearly with increasing flow rates, and increasing concentrations of ethylene. Zirconia-titania pellet size and heel depth had little effect on oxidation of ethylene. Platinizing the zirconia-titania significantly increased ethylene oxidation. The catalyst was found to absorb large quantities of water when the humidity of the air stream was elevated and this greatly decreased catalytic activity.